1. Technical field
The invention relates to vehicle suspensions and particularly to an air spring having an internal sealing ring which clamps and forms an air-tight seal with an end of a tubular elastomeric sleeve against the inner surface of an end cap. More particularly, the invention relates to such an air spring in which an external clamping band restricts the outward expansion of the end cap sidewall to maintain the air-tight seal with the elastomeric sleeve within the interior of the open end of the end cap.
2. Background Information
Pneumatic springs, commonly referred to as air springs, have been used for motor vehicles for a number of years to provide cushioning between movable parts of the vehicle, primarily to absorb shock loads impressed on the vehicle axles by the wheels striking an object in the road or falling into a depression. The air spring usually consists of a flexible rubber sleeve or bellows containing a supply of compressed fluid and has one or more pistons located within the flexible resilient sleeve. The piston causes compression and expansion of the fluid within the sleeve as the vehicle experiences the road shocks. The spring sleeve is formed of a flexible elastomeric material which permits the piston and end cap to move axially with respect to the sleeve and within the interior of the sleeve.
The ends of the sleeves are sealingly connected to the piston and an opposite end cap, if only one piston is used in the particular spring construction. The clamping of the ends of the flexible sleeve onto the piston and end cap is one of the important and major assembly steps in the production of air springs. Heretofore, the usual manner of sealing the sleeve against the piston and end cap has been by clamping an exteriorly located metal ring against the flexible sleeve which crimps and squeezes the rubber material thereof against a sealing surface of the piston or end cap. These prior art sealing methods and structures require a permanent deformation of the sealing ring and require equipment to supply sufficient pressure to the metal sealing ring to permanently deform the metal upon crimping it radially inwardly against the sealing surface of the adjacent air spring member.
Many of these problems have been eliminated by the improved air spring constructions and sealing arrangements shown in U.S. Pat. Nos. 4,787,607 and 4,793,598, which are assigned to the same assignee as is the present invention. Although the constructions of these specifically mentioned patents are suitable for most air spring applications, it is desirable that for certain applications, especially those using an extremely high internal fluid pressure within the flexible sleeve and where certain design applications eliminate the integral molded hoop-type reinforcement flange which extends about the open end of the end cap, to ensure the integrity of the air-tight clamping engagement of the internal sealing ring with the internal surface of the end cap, and to prevent creep of the end cap material from effecting the seal between the sealing ring and sleeve end, that a positive mechanical device be provided to resist forces which are generated by the inflated sleeve and to prevent creep of the cap material.
Although various types of sealing and clamping arrangements have been devised for forming the air-tight seal between the open ends of the flexible sleeve and with the end cap assembly and/or piston member of an air spring, none of the known prior art is believed to enhance the sealing engagement there between by the use of an external clamping band. Other examples of prior art air spring elastomeric sleeve sealing arrangements, in addition to the above two cited U.S. patents, are shown in U.S. Pat. Nos. 4,784,376: 4,787,606 and 4,564,177. However, none of these prior air springs use or suggest any type of external clamping band to enhance the internal seal.
Therefore the need exists for certain air spring applications, to provide a positive mechanical lock for restricting outward expansion of the annular sidewall of the end cap and possible creep of the cap material, to ensure the integrity of the air-tight seal formed within the open end of the end cap in air spring applications.